Deviance

n. aberration, abnormality, berrancy; unacceptable behavior

Deviance can refer to any of several topics, including:Deviant behavior in social sciencesstatistical deviance—see  deviance (statistics)
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Deviant /de·vi·ant/ 1. varying from a determinable standard. 2. a person with characteristics varying from what is considered standard or normal. [more]Deviance - Community and Resources

Noun
1. a state or condition markedly different from the norm
(synonym) aberrance, aberrancy, aberration
(hypernym) abnormality, abnormalcy, abnormal condition
(hyponym) chromosomal aberration, chromosomal anomaly, chrosomal abnormality, chromosonal disorder
2. deviate behavior
(synonym) deviation
(hypernym) abnormality, irregularity

To evaluate the goodness of fit of a generalized linear model , a common statistic that is computed is the so-called Deviance statistic. It is defined as:
Deviance = -2 * (Lm - Ls)
where Lm denotes the maximized log-likelihood value for the model of interest, and Ls is the log-likelihood for the saturated model, i.e., the most complex model given the current distribution and link function . For computational details, see Agresti (1996).
See also the description of Generalized Linear Models .